Generally, a user in a vehicle has no choice but to open a window, a front door or a rear door of the vehicle to converse with a person outside the vehicle while an air conditioner or a heater inside the vehicle is turned on in hot summer or cold winter.
That is, if an air conditioner is turned on in hot summer or a heater is operating in cold winter and windows and doors of the vehicle are closed, sounds of the vehicle are not transferred to the inside or outside of the vehicle, and a driver or a passenger, therefore, should open a window or a door inevitably to converse with a person outside the vehicle.
In a conventional vehicle like this, since a driver or a passenger should open a window or a door every time to converse with a person outside the vehicle from the inside, cold or warm air in the vehicle is discharged to the outside in summer or cold winter, and thus fuel consumption is increased, and in addition, it is inconvenient in that a window or a door should be opened frequently whenever the driver or the passenger converses with a person outside the vehicle.
In addition, a surround warning device used in a conventional vehicle has a problem in that since it transfers a warning signal to a driver or a pedestrian in the vicinity using a lamp or a sound, a hearing-impaired person may not hear the sound, and collision accidents frequently occur due to the reason.